The present invention relates in general to a winding and tightening tool which is used for tightening a pre-formed coil on a self-locking retainerless dental matrix.
A winding tool of this type was introduced by the present inventor in his previous U.S. Pat. No. 3,435,905 issued Apr. 1, 1969 and entitled TOOL AND METHOD OF MANUFACTURING THE SAME.
Retainerless dental matrices which include a pre-formed coil and which can be tightened by such a tool are disclosed in the inventor's previous U.S. Pat. Nos. 3,411,214 granted Nov. 19, 1968 and 3,921,299 granted Nov. 25, 1975.
These matrices are made of stainless steel. A selected amount of torque is applied in winding the coil to fully engage and lock the matrix on the tooth. Thereafter, the winding tool is disengaged from the coil and removed from the mouth, thereby, the matrix is locked on said tooth and does not require a retainer to keep it locked thereon, as with other matrices. Retainerless matrices provide greater field of vision and a freer uncluttered operative field for the dentist.
In order to control the required amount of torque, and to avoid applying too much torque to the coil and the matrix itself, and thereby damaging the matrix, the inventor introduced an improvement in his winding tool which is disclosed in U.S. Pat. No. 3,852,884 granted Dec. 10, 1974 and entitled WINDING AND TIGHTENING TOOL AND METHOD OF MANUFACTURING SAME. This winding tool included torque limiting means in the form of spring loaded balls which were engagable in an opening or sockets in the handle for transmitting torque from a handle of the winding tool to the winding member at the tip of the winding tool. When the torque experienced at the winding tip exceeds a selected amount the barrel stops rotating, and the spring loaded ball is depressed by the edge of said rotating socket, thereafter the ball is dislodged from said socket so that torque is no longer conveyed to the barrel or the winding member. In this way excess torque damage to the retainerless dental matrix is avoided, as well as preventing undue torque from being uncomfortably applied to the patient's tooth being restored, as is the case with retainer-type matrices which do not provide torque control.
The present inventor has also disclosed a retainerless dental matrix of the foregoing type which, rather than being made of stainless steel, can be made of plastic. One major advantage of this is that the plastic can be transparent so that light-curable dental restorative materials can be used behind a clear transparent plastic film matrix and set, using said light. The curing light of course can be transmitted through the transparent plastic matrix to cure the material behind the matrix. As with the steel retainerless matrix, this plastic retainerless matrix requires the torque control of this dual torque device of this invention, at a lower torque.
This plastic retainerless dental matrix is disclosed in the inventor's co-pending application having U.S. Ser. No. 586,569, filed Mar. 6, 1984 and now U.S. Pat. No. 4,523,909 issued 6/18/85 entitled PLASTIC DENTAL MATRIX AND METHOD OF MANUFACTURING SAME.
The foregoing patents and patent application to the present inventor are incorporated here by reference.
In developing the plastic dental matrix, the inventor found that several problems had to be overcome which were related to the difference in material strength and other characteristics of plastic as opposed to stainless steel. The inventor also found that a lower amount of torque was necessary for winding the coil of the plastic matrix than the coil of the stainless steel matrix, so as to avoid self destructive tearing of the plastic matrix during use and prior to serving its intended useful purposes, as could occur with high torque.
While the inventor's previous winding tool as disclosed in above identified U.S. Pat. No. 3,852,884, had a mechanism for setting a selected torque, only a single torque setting could be obtained.